A topology refers to the arrangement or the physical placement of network components of a computer network. As network topologies, there are various topologies such as a cascade topology, a star topology, and a ring topology.
The cascade topology (daisy-chain) has been generally used for relay system. In the cascade topology, when a defect occurs in at least one of remote units, it may be difficult to provide services in all relays serving as lower layers.
In order to solve the problem, there is a method in which when abnormality occurs in a certain remote unit, the remote unit optically passed by providing a passive optic switch in the relay system, or a method in which relays system are configured as a ring topology using redundancy fiber.
Unfortunately, in the method using the passive optic switch, since a separate module is needed, cost may increase. Further, in the ring topology using the redundancy fiber, since photoelectric and electro-optic devices, input/output ports, and redundancy fiber infrastructure are needed twice more than those in the relay according to the related art, cost may increase.
An embodiment of the inventive concept is directed to an optical relay capable of switching Tx/Rx (transmitter/receiver) functions without using redundancy fiber even when a defect occurs in a certain optical relay by being configured as a ring topology.